Diaphragm for acoustic apparatus



M. HEPNER.

DIAPHRAGM FOR ACOUSTIC APPARATUS. APPLICATION- FILED FEB. a, 192:.

I,&35,843. A Patented Nov. 14, 1922.;

114072 iz'fi m r I Hw,

Patented Nov. 14, 1922.

1,435,843 PATENT OFFICE.

UNITED STATES MORITZ HEPNER, OF BERLIN, GERMANY, ASSIGNOR TO THE FIRM JAROSLAWS ERSTE GLIMME RWAREN-FABRIK IN BERLIN, OI BERLIN, GERMANY.

DIAPHRAGM FOR ACOUSTIC APPARATUS.

Application filed February 3, 1921.

To all whom it may concern:

Be it known that I, Monrrz HEINER, merchant, citizen of Germany, residing at Berlin, in Prussia, Germany, have invented new and useful Improvements in Diaphragm for Acoustic Apparatus, of which the following is a specification.

Diaphragms for acoustic apparatus, e. g. sound cases for phonographs, telephones, microphones and the like, are preferably made from mica by punching or turning, as this material combines the required acoustic properties, particularly a high sensitiveness for the sound and a resonance free from extraneous noises, with the required mechanical resistance and with absolutely uniform structure. This invention has for its purpose to economize this expensive material in using as mica disks or mica diaphragms, plates which are composed of several thin mica blades, said plates presenting the same appearance and possessing the same quality and the same acoustic properties as the mica plates made in one piece. This object is attained according to the invention by composing the diaphragms of several thin plates of mica which either are of the total area of the diaphragm or are individually composed of portions which make up together the total area of the diaphragm, said thin plates being connected. the one with the others under heat and pressure by means of varnish in such a manner that they form together a rigid body. Formerly such plates of mica which were thinner than the diaphragm could be used only for second ary purposes. Owing to this invention it has become possible to utilize this waste ma terial just as well as the other thick pieces of mica which are adapted to be worked directly for forming diaphragms.

The inner layers of the diaphragm are preferably composed of two or more pieces in the shape of a segment or of a sector, said pieces forming together a circle. It is advisable to dispose the segments of the inner layers eccentrically that is to say to arrange the same in such a manner that their edges do not reach to the center of the diaphragm, so that the diaphragm can be perforated at the center, as is necessary for certain purposes, without touching the edges of the pieces. Cellon varnish is preferably used as agglutinant, this varnish which is a solution f acctyl-cellulose possessing, after Serial No. 442,237.

it has hardened, almost the same elasticity as the mica. It is therefore possible to produce with the aid of this varnish a diaphragm which does not differ, as regards resonance and appearance, from a diaphragm made in one piece. i

It has already been proposed to compose dlaphragms of several layers of mica in order to obtain determined differences in resonance. But in this case there are not used thin lamels but disks of mica of which each is of the usual thickness of the diaphragms. In these composed diaphragms of known type the different layers are not combined to form a rigid whole and they are not of different sizes so that the layers do not make up together the total area of. the diaphragm. There is not obtained any saving of mica as is the case according to this invention but quite on the contrary much more mica material is used.

In the accompanying drawing two forms of construction of the object of the invention are shown by way of example.

The form of construction shown in Fig. 1 consists of five layers which are separately shown in Figures 2 to 6. As can be seen from the drawing, the upper and lower layer consist each of a full circle, the three intermediate layers being each composed of two unequal segments. The angle for which the third layer is displaced with regard to the second layer and the fourth layer with re-- gard to the third layer can be chosen at will.

In the form of construction shown in Fig. 7 the diaphragm is composed of four layers (Figures 8 to 1],) the upper and lower layer forming a full circle and the two intermediate layers consisting each of two semicircular lamels. The joint in the third layer is also displaced with regard to the joint in the second layer. In this diaphragm the parts of which the intermediate layers are composed are not arranged eccentrically so that the joints pass through the center of the diaphragm. In this form of construction there could be used also more than two intermediate layers. Each of the intermediate layers could consist eventually of three sectors, of which each includes an angle of 120, or even of four quadrants, and so forth. The resonance and. theother acoustic properties of the diaphragm can be varied at will. by reducing the number of layers and by altering the position of the intermediate layers.

Transparent varnishes are used as agglutinants. Cellon varnish has proved to be a specially good agglutinant.

The manufacturing of the diaphragm is effected in such a manner that after the layers have been stuck together the diaphragm is clamped in a holdfast and heated under pressure to approximately 170 C. This diaphragm is of clear sound, free from blisters and flows, transparent and of plane surface.

Having now particularly described and ascertained the nature of my said invention, I declare that what li claim is:

1. A diaphragm for acoustic instruments, consisting of several layers of thin blades of mica, the blades of at least one layer combining to form a plane disk of uniform thickness and of the full area of the diaphragm, the blades of said layers being united together by means of varnish under heat and pressure.

2. A diaphragm for acoustic instruments, consisting of several layers of thin blades of mica, the outer layers forming each a plane disk of the full area of the diaphragm, the intermediate layers being individually composed of two or more portions which combine to form plane disks of uniform thickness and of this full area, these disks being united together by means of varnish under heat and pressure.

3. A diaphragm for acoustic instruments, consisting of several layers of thin blades of mica, the layers forming each a plane disk of the full area of the diaphragm, the intermediate layers being individually composed of two or more segments which are arranged eccentrically and combined to form plane disks of uniform thickness and of this full area, these disks being united together by means of varnish under heat and pressure.

4. A diaphragm for acoustic instruments, consisting of several layers of thin blades of mica, the layers forming each a plane disk of uniform thickness and of the full area of the diaphragm and being united together by means of cellon varnish.

5. A diaphragm for acoustic instruments, consisting of several layers of mica, at least one layer consisting of a thin blade of mica of the full area of the diaphragm, the other layers being composed individually of at least two portions of thin-micablades, the edges of which tightly touch and which combine to form a plane disk of this full area and of uniform thickness throughout, all layers being united together to form a rigid body of uniform thickness by means of varnish. under heat and pressure.

6. A diaphragm for acoustic instrun'ients. consisting of several layers of mica, at least one layer being composed. of several portions of the same thickness, which combine to form the full size and area of the diaphragm, these portions being united togetherand with the other layers by means of varnish.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

MORITZ HEPNER.

Vitnesses HERMANN HAUPERT, AeNns STRUCK. 

